The present invention relates to airbags and sensors used to control airbag deployment in general and to sensors which monitor the actual deployment sequence in particular.
While airbags were originally developed as a passive restraint system, experience has shown that airbags work best in combination with seatbelts and other safety systems. Although airbags contribute to the overall safety of occupants of an automobile, they can present a danger to an occupant who is positioned too close to an airbag when it deploys. This condition, where the occupant is positioned so that airbag deployment might be dangerous, is referred to as the occupant being xe2x80x9cout of positionxe2x80x9d. Various systems have been developed to detect an xe2x80x9cout of positionxe2x80x9d occupant. Sensor systems designed to detect the occupant""s position often require constant monitoring so that in the event of a crash the occupant""s position is known. Sensor systems designed to detect the position of the occupant have been proposed based on ultrasound, optical, or capacitance sensors. Constant monitoring of sensors, which may have high data rates, requires the design of algorithms which can reduce sensor data to a single condition or a limited number of data conditions which are used in an airbag deployment decision to prevent airbag deployment or for a duel stage airbag to select the level of deployment. Maintaining data integrity between the non-crash positional data, and the noisy environment produced by a crash requires additional processor capabilities and algorithm development with associated testing.
One known approach for determining if a vehicle occupant is too close to the airbag is set forth in U.S. Pat. No. 6,094,610 wherein a plurality of capacitive sensors mounted on the steering wheel are used to detect the distance between the cover of an airbag and the seat occupant. U.S. Pat. No. 6,254,127 describes a variety of approaches for determining the distance between an airbag module or cover, and a vehicle occupant so as to avoid injuring an occupant who is out of position, i.e., too close to the airbag module.
These prior art approaches attempt to determine, based on various sensors, the distance between the airbag and the passenger before the airbag is deployed. In many instances the vehicle occupant will not be too close to the airbag at the time the decision to deploy the airbag is made, but, because of the rate at which the occupant is approaching the airbag the occupant will be too close when the airbag is actually deploying. To handle these situations, more sophisticated sensors and algorithms are needed to attempt to predict the occupant""s position when the airbag is actually deployed or nearly completely deployed. In other words, the ideal airbag deployment system functions such that the airbag deploys fully or nearly fully before the occupant engages the airbag. Existing systems inhibit airbag deployment when, based on various sensors and algorithms, it is determined that because of the position of the vehicle occupant the bag is more likely to harm than to benefit the occupant. Successfully creating a sensor and algorithm system is complicated inasmuch as there is usually very little delay between the decision to deploy and the actual deployment. This is so because the maximum benefit from an airbag is achieved by early deployment, and at the same time, more time before deployment maximizes the information available to determine whether deployment is necessary. The desire to maximize effective deployment of the airbags while minimizing unnecessary deployment creates a tension between waiting for more information and deploying immediately. Therefore, once sufficient information is available, deployment typically follows nearly immediately.
Therefore, a system which employs occupant position sensors and algorithms must be able to supply at all times an indication of whether airbag deployment should be inhibited so that the inhibit decision can be applied whenever the airbag deployment decision occurs. This means the sensors and algorithms used to develop the occupant position inhibit signal cannot be optimized to deal with a specific time frame in which the actual deployment decision is made. The end result is that such algorithms may be less accurate than desired because they must predict events relatively far in the future-perhaps tens of milliseconds. One known type of sensor employs a tape which extends between the front of the airbag and a sensor mounted on the airbag housing. The sensor monitors the rate at which tape is withdrawn from the sensor and can detect airbag impact with a vehicle occupant by a decrease in acceleration as measured by the rate of tape withdrawal from the sensor. In the event that the airbag is insufficiently deployed when bag contact is detected, the airbag is vented. Such prior art sensors are limited to detecting the bag interaction with a vehicle occupant, and cannot detect the occupant before the airbag engages the occupant. What is needed is a sensor and a mechanism responsive to the sensor which can effect airbag deployment shortly before the airbag interacts with the vehicle occupant.
The vehicle occupant position sensor of this invention is mounted on the front of an airbag which is deployed toward a vehicle occupant. The sensor is comprised of one or more capacitance sensors constructed by rendering portions of the airbag which face the vehicle occupant conductive. Such a sensor can be constructed by painting portions of the airbag with conductive paint. Electrical leads are connected to the capacitive sensor using wires or, preferably, conductive traces painted on the airbag, preferably on the inside of the airbag and connecting through the airbag fabric to the capacitive sensor on the outside of the airbag. A sensor is six inches in diameter and can be used to detect an occupant as much as 12 inches away from the sensor. The airbag on which the sensor is placed is also constructed to allow venting of the airbag before it is fully deployed. An electronic system uses the capacitive sensor to continually determine the distance between the sensor and the vehicle occupant, and to determine the velocity and acceleration of the vehicle occupant with respect to the sensor. The output of the capacitive sensor mounted on the airbag may be used by various safety systems within the vehicle, such as belt retractors, to react to the actual motions of the vehicle occupant during a crash. Advantageously, the output of the capacitive sensors as processed by a control system is used to predict the interaction between the airbag and the vehicle passenger and to cause the airbag to be vented if that interaction is predicted to be more harmful than beneficial to the vehicle occupant. Because venting the airbag renders the airbag ineffectual, whether for good or bad effect, a system which prevents airbag venting once the airbag is inflated or nearly inflated is incorporated into the sensor, control system, or venting system.
An alternative embodiment of the invention employs a conductive portion of the bag facing the occupant, together with a conductive portion of the seat on which the occupant sits. When the conductive portion of the bag contacts the occupant, the presence of the occupant is detected directly by means of an electrical circuit which includes the vehicle occupant. Another alternative embodiment employs a sensor which transmits electromagnetic radiation such as microwaves at a target moving with the front of the airbag. The sensor detects when the airbag decelerates due to the bag and target impacting the vehicle occupant. In both the foregoing embodiments, the airbag is vented if the airbag impacts the vehicle occupant too soon to provide a benefit.
It is a feature of the present invention to provide an airbag and deployment system which incorporates an occupant position sensor mounted on the airbag.
It is a further feature of the present invention to provide a mechanism for venting an airbag before the airbag is fully inflated.
It is another feature of the present invention to provide an airbag venting system which cannot be operated once the airbag reaches a certain stage of deployment.
It is a yet further feature of the present invention to provide a means whereby the airbag deployment decision may be inhibited after airbag deployment has begun.
It is a still further feature of the present invention to provide an occupant position sensor mounted on the airbag which provides input to other safety systems within the vehicle.
Further features, and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings.